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In this article, we report a tungsten disulphide (WS2) nanosheet sensing platform based on chemiluminescence resonance energy transfer (CRET) for light on detection of ochratoxin A (OTA). The CRET system involves OTA aptamer-12-mer linker-DNAzyme, phosphate-DNA, lambda exonuclease (λexo), hemin, H2O2, luminol and a WS2 nanosheet. Based on the change in chemiluminescence intensity resulting from the OTA aptamer-12-mer linker-G-Quadruplexes/Hemin DNAzymes affinity for or desorption from the WS2 nanosheet surface in the presence and absence of OTA, an ultra-sensitive CRET-based sensor system is proposed, in which the OTA aptamer-12-mer linker-G-Quadruplexes/Hemin DNAzymes–H2O2–luminol and WS2 nanosheets act as CRET donors and acceptors, respectively. Various factors affecting the detection of OTA, including the incubation time of the OTA aptamer-12 mer linker-G-Quadruplexes/Hemin DNAzyme and WS2 nanosheet, the amount of λexo, concentrations of the WS2 nanosheet, luminol and H2O2, and pH value of the chemiluminescence reaction solution were investigated in detail. Under the optimal experimental conditions, the relative luminesecence intensity of the sensing system exhibited a good linear correlation with the OTA concentration in the range of 1.0–10.0 ng mL–1 with a LOD of 0.13 ng mL–1. The proposed CRET-based sensing system also exhibited excellent recoveries of 85.7–93.0% in rice samples and showed good application prospects for the analysis and detection of OTA, which is also easily extended to assay other biomolecules by simply changing the recognition sequence with the substrate aptamer.

Microporous aluminum-based metal-organic frameworks (CAU-1) are used to develop a simple and sensitive electrochemical sensor for myricetin (MYR) based on a modified carbon paste electrode (CPE) for the first time. The morphologies and electrochemical properties of the as-synthesized CAU-1 are studied utilizing various analytical methods including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, N

Due to their outstanding properties, bioadhesive hydrogels have been extensively studied by researchers in recent years. By designing the properties of bioadhesive hydrogels, they can be reasonably applied to biomedicine. Therefore, this practicality has prompted the birth of many bioadhesive hydrogels with excellent properties. In this review, by studying the progress in the field of bioadhesive hydrogels, we summarized the properties of hydrogels in bioadhesion, including adhesion, biocompatibility, degradability and antibacterial properties. In addition, we also summarized the applications of bioadhesive hydrogels in wound dressings, tissue repair, cell adhesion and wearable sensors. Finally, we summarized and outlooked the research on bioadhesive hydrogels, hoping to provide a valuable reference for the progress in the field of bioadhesive hydrogels.

Graphical abstract, Highlights • This review describes the principle of the bio-barcode assay (BCA) and provides a comparison of method applications. • The review summarizes the application of BCA for the detection of macromolecules. • It summarizes the applications of BCA technology for small–molecule detection in recent years. • BCA technology makes up for the shortcomings of other technologies. • It summarizes the feasibility, deficiencies and expectations of BCA technology., With the rapid development of nanotechnology, the bio-barcode assay (BCA), as a new diagnostic tool, has been gradually applied to the detection of protein and nucleic acid targets and small-molecule compounds. BCA has the advantages of high sensitivity, short detection time, simple operation, low cost, good repeatability and good linear relationship between detection results. However, bio-barcode technology is not yet fully formed as a complete detection system, and the detection process in all aspects and stages is unstable. Therefore, studying the optimal reaction conditions, optimizing the experimental steps, exploring the multi-residue detection of small-molecule substances, and preparing immuno-bio-barcode kits are important research directions for the standardization and commercialization of BCA. The main theme of this review was to describe the principle of BCA, provide a comparison of its application, and introduce the single-residue and multi-residue detection of macromolecules and single-residue detection of small molecules. We also compared it with other detection methods, summarized its feasibility and limitations, expecting that with further improvement and development, the technique can be more widely used in the field of stable small-molecule and multi-residue detection.

An ultrasensitive bio-barcode competitive immunoassay method based on droplet digital polymerase chain reaction (ddPCR) was developed for the determination of triazophos. Gold nanoparticles (AuNPs) were coated with monoclonal antibodies (mAbs) and complementary double-stranded DNA (dsDNA), which included bio-barcode DNA and thiol-capped DNA. Magnetic nanoparticle (MNP) probes were constructed by modifying the MNPs with ovalbumin-hapten conjugates (OVA-hapten). The target pesticide and OVA-hapten on the surface of the MNP probes competed with the AuNP probes simultaneously, and then the bio-barcode DNA was released for quantification by ddPCR. The concentration of released DNA was inversely proportional to the concentration of pesticide to be tested. Under the optimum conditions, the competitive immunoassay exhibited a wide linear range of 0.01-20 ng/mL and a low detection limit of 0.002 ng/mL. Spike recovery tests were carried out using apple, rice, cabbage, and cucumber samples to verify the feasibility of the method. The recovery and relative standard deviations (RSDs) of the technique ranged from 76.9 to 94.4% and from 10.8 to 19.9%, respectively. To further validate the results, a linear correlation analysis was performed between the proposed method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Consequently, the bio-barcode immunoassay based on nanoparticles and ddPCR, an ultrasensitive method, showed great potential for the determination of target pesticides in real samples.

Purpose The purpose of this paper is to investigate the tribological effects of laser surface texturing (LST) and residual stress on functional surfaces. Design/methodology/approach Three different surface textures (circular dimple, elliptical dimple and groove) with two different textured area ratios (10 and 20 per cent) are designed and fabricated by a Picosecond Nd YAG Laser machine. The friction and wear performance of textured specimens is tested using a UMT-2 friction and wear testing machine in mixed lubrication. Findings Test results show that elliptical dimples exhibit the best performance in wear resistance, circular dimples in friction reduction and grooves in stabilization of friction. The surfaces with larger textured area density exhibit better performance in both friction reduction and wear resistance. The improved performance of LST is the coupled effect of surface texture and residual stress. Originality/value The findings of this study may provide guidance for optimal design of functional surface textures in reciprocating sliding contacts under mixed or hydrodynamic lubrication, which can be used in automotive and other industrial applications.

Herein, a novel visual method for detecting triazophos based on competitive bio-barcode immunoassay was described. The competitive immunoassay was established by gold nanoparticles (AuNPs), magnetic microparticle (MMPs) and triazophos, combined with biochip hybridization system to detect the residual of triazophos in water and apple. Because AuNPs carried many bio-barcodes, which hybridized with labeled DNA on the biochip, catalyzed signal amplification using silver staining was detected by grayscale values as well as the naked eye. Notably, the grayscale values decreases with increasing the concentrations of triazophos, and the color change weakened gradually. The detection range was in between 0.05 and 10 ng/mL and the minimum detection limit was set at 0.04 ng/mL. Percent recovery calculated from spiked water and apple samples ranged between 55.4 and 107.8% with relative standard deviations (RSDs) of 12.4–24.9%. It has therefore been shown that this protocol provides a new insight for rapid detection of small molecule pesticides in various matrices.

A molecularly imprinted polymer (MIP) with specific adsorption for patulin was successfully polymerized by precipitation polymerization using 2-oxindole (2-oxin) and 6-hydroxynicotinic acid (6-HNA) as dummy template molecules, methylacrylic acid (MAA) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a crosslinker, 2,2-azobis-(2-methylpropionitrile) (AIBN) as a initiator, and methanol as a porogen solvent. The molecularly imprinted solid phase extraction (MI-SPE) column was prepared using the polymer as a sorbent and applied for the selective extraction of patulin from real samples. The results showed that the MI-SPE method had high selectivity and specific adsorption towards patulin with mean recoveries ranged between 81.3% and 106.3% and a relative standard deviation (RSD) 0.998. The limits of detection (LODs, S/N = 3) were 0.05–0.2 ng g−1, and the limits of quantification (LOQs, S/N = 10) were 0.2–0.5 ng g−1. The developed method showed a better purification and higher patulin recovery for real samples than the quick, easy, cheap, effective, rugged, safe “QuEChERS” method.

A competitive bio-barcode immunoassay is described for the trace detection of parathion in water, pear, cabbage, and rice samples. It is based on amplification by platinum nanoparticle acting as a nanozyme. Gold nanoparticles (AuNPs) were modified with (a) monoclonal antibodies (mAbs) against parathion, and (b) thiolated single-stranded DNA (ssDNA) oligonucleotides. Magnetic nanoparticles (MNPs) were functionalized with ovalbumin coupled with parathion hapten. Parathion and its hapten compete with mAbs on the surface of the AuNPs. Subsequently, the platinum nanoparticles (PtNPs) probe, which was functionalized with the complementary thiolated ssDNA (C-ssDNA), was added to the reaction mixture for the detection of parathion. The signal was catalytically amplified by coupling with platinum nanozyme using teramethylbenzidine and H2O2 as the chromogenic system. The immunoassay has a linear range that extends from 0.01–50 μg·L−1, and the limit of detection is 2.0 × 10−3 μg·L−1. The recoveries and relative standard deviations (RSDs) ranged from 91.1–114.4% and 3.6–15.8%, respectively. The method correlates well with data obtained by gas chromatography-tandem mass spectrometry (GC-MS/MS).

We aim to develop a solid-phase extraction (SPE) based on a dummy molecularly imprinted polymer (MIP) and liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) for selective determination of four pyridine carboxylic acid herbicides (aminopyralid, picloram, fluroxypyr, and clopyralid) in milk samples. Using picloram as the dummy template, MIP nanocomposites with highly selective recognition and adsorption for the target molecule and its structural analogs were successfully synthesized by precipitation polymerization. Adsorption isotherms and kinetics were used to determine the adsorption performance and specific recognition mechanism of both MIPs and non-molecularly imprinted polymers (NIP). The Scatchard plot analysis revealed that two different binding sites were formed in the MIP with maximum binding capacity (Qmax) of 1171.8 μg·g−1 and 3022.5 μg·g−1, respectively. Recovery at three spiking levels of 10, 20, and 50 μg·L−1 ranged between 75.3 and 89.8% with relative standard deviations (RSDs)

Herein, we developed a multi-analyte fluorescence immunoassay for detection of three organophosphate pesticides (triazophos, parathion, and chlorpyrifos) in various agro-products (rice, wheat, cucumber, cabbage, and apple) using fluorescently labeled oligonucleotide and gold nanoparticle (AuNP) signal amplification technology. The AuNP probes for the three analytes were constructed by simultaneously modifying the corresponding antibodies and fluorescently labeled oligonucleotides on the probe surface. Three fluorophores (6-FAM, Cy3, and Texas red) with high fluorescence intensity and little overlap of excitation/emission wavelengths were selected. The method showed satisfactory linearity for triazophos, parathion, and chlorpyrifos in the ranges of 0.01–20, 0.05–50, and 0.5–1000 μg/L, respectively. For the 3 analytes, the limits of detection (LODs) were 0.007, 0.009, and 0.087 μg/L, respectively. The average recoveries were 77.7–113.6%, with relative standard deviations (RSDs) of 7.1–17.1% in various food matrices. The proposed method offers great potential in food safety surveillance, and could be used as well as a reference for multi-residue analysis of other small-molecule contaminants.

In this study, a novel magnetic molecularly imprinted polymer (MMIP) was prepared by surface imprinting technology using 2-oxin and 6-HNA as dual virtual templates and 4-vinyl pyridine (4-VP) as the functional monomer for extraction of patulin (PAT) from the surface of magnetic nanoparticles. MMIPs were characterized by fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The results showed that the molecularly imprinted polymer (MIP) was successfully coupled with magnetic nanoparticles and could be used as a magnetic selective recognition material. Moreover, MMIPs have a greater adsorption capacity for PAT than conventional MIPs. The magnetic dispersion solid-phase extraction procedure was optimized and then combined with liquid chromatography-tandem mass spectrometry (MDSPE-LC-MS/MS) for detection of PAT in juice samples. The method showed excellent analytical performance in terms of linearity (ranged between 0.5 μg L−1 and 100 μg L−1with correlation coefficients (r) higher than 0.999) and limit of detection (LOD) (0.1 μg L−1, S/N = 3). At three spiking concentrations (1, 10, and 50 μg L−1), the mean recoveries were ranged between 79.4% and 97.9% with relative standard deviations (RSDs)

A straight-forward analytical strategy called internal extractive electrospray ionization mass spectrometry (iEESI-MS), which combines solvent extraction of chemicals inside a bulk sample with in situ electrospray ionization mass spectrometry, has been established to directly characterize the interior of a bulk sample with molecular specificity. The method allows both qualitative and quantitative analysis of analytes distributed in a 3-dimensional volume (e.g., 1 ~ 100 mm(3)) of various synthetic and biological matrices (e.g., chewing gum, leaves, fruits, roots, pork, lung tissues) without either mashing the sample or matrix separation. Using different extraction solvents, online chromatographic separation of chemicals inside the sample volume was observed during iEESI-MS analysis. The presented method is featured by the high speed of analysis, high sensitivity, low sample consumption and minimal sample preparation and/or degradation, offering unique possibilities for advanced applications in plant science, clinical diagnosis, catalyst studies, and materials science.

Chronic inflammation induced by endotoxin from a dysbiotic gut microbiota contributes to the development of obesity-related metabolic disorders. Modification of gut microbiota by a diet to balance its composition becomes a promising strategy to help manage obesity. A dietary scheme based on whole grains, traditional Chinese medicinal foods, and prebiotics (WTP diet) was designed to meet human nutritional needs as well as balance the gut microbiota. Ninety-three of 123 central obese volunteers (BMI ≥ 28 kg m(-2) ) completed a self-controlled clinical trial consisting of 9-week intervention on WTP diet followed by a 14-week maintenance period. The average weight loss reached 5.79 ± 4.64 kg (6.62 ± 4.94%), in addition to improvement in insulin sensitivity, lipid profiles, and blood pressure. Pyrosequencing of fecal samples showed that phylotypes related to endotoxin-producing opportunistic pathogens of Enterobacteriaceae and Desulfovibrionaceae were reduced significantly, while those related to gut barrier-protecting bacteria of Bifidobacteriaceae increased. Gut permeability, measured as lactulose/mannitol ratio, was decreased compared with the baseline. Plasma endotoxin load as lipopolysaccharide-binding protein was also significantly reduced, with concomitant decrease in tumor necrosis factor-α, interleukin-6, and an increase in adiponectin. These results suggest that modulation of the gut microbiota via dietary intervention may enhance the intestinal barrier integrity, reduce circulating antigen load, and ultimately ameliorate the inflammation and metabolic phenotypes.

In this paper, we consider the problem of joint relay selection and power allocation in a cognitive radio (CR) network, where a secondary user (SU) source communicates with a secondary access point (AP) assisted by a set of SU relays. Each SU in this set not only acts as a potential relay but also has its own data transmission requirement. Keeping the interference to the primary user (PU) below a specified limit, we propose an optimal scheme with quality of service (QoS) support. On the premise of meeting the minimum transmission rate requirements of all SUs, the goal of the proposed scheme is to maximize the weighted sum rate of the network under transmission power and energy constraints. A closed-form solution for the optimal power allocation between the source and the relay can be obtained by the Karush-Kuhn-Tucker (KKT) conditions. Furthermore, simulation results and comparisons are presented to illustrate the performance of the proposed scheme.

In cognitive radio network, sensing based spectrum sharing access (SSA) is proposed as a hybrid spectrum access scheme of opportunistic spectrum access (OSA) and spectrum sharing access. In this paper, we study the power and channel allocation under the hybrid spectrum access in multiple secondary user (SU) environment. Considering not only the interference caused to primary user (PU) and the average transmit power constraints, but also the different traffic demand of SUs and the interference among SUs existed in multiple SU environments, a distributed channel and power allocation algorithm are proposed to maximize the system throughput while satisfying the QoS of SU transmissions. With these inequality constraints, Lagrange dual composition method is introduced for this nonlinear optimization problem. Exact expressions of power allocation and the channel allocation scheme are derived under power and interference limits and QoS demands. Simulation results are presented to verify the influencing factors and advantage of the proposed algorithm compared to opportunistic spectrum access.

Carrier aggregation is one of the most distinct features of 4G systems including LTE-A (Long Term Evolution Advanced), which is being standardized in 3GPP as part of LTE Release 10. The closed-loop concept with codebook based precoding MIMO (multiple-input multiple-output) and transmission mode selection, termed as RI (rank indicator) selection, have been deployed in LTE-A systems to provide high system performance required by 4G systems. This article focuses on the study of adaptive transmission mode selection in LTE-A carrier aggregation scenarios. We propose an adaptive transmission mode selection scheme using average channel capacity and BER to maximize the average spectral efficiency (ASE) with a given target bit error ratio (BER). Numerical results demonstrate improvement over each fixed modern terms of average spectral efficiency.

Based on the actual operation of the system and QoS status, the 3G mobile network optimization consists of system dynamic testing, analysis and adjustment to the existing system configuration to provide the highest QoS, the optimum coverage and the lowest network cost-effective. Capacity planning and pilot pollution are two of the key issues in CDMA network optimization. By coverage optimization, power control, access control, network capacity can be improved. And eliminating RF pollution by parameters adjustment can furtherly improve performance of CDMA network.

Extractive electrospray ionization of 1-hydroxypyrene (1-OHP) is achieved by using non-polar solvents (e.g., benzene, toluene, xylene, pentane and hexane) as the primary ESI solvent. The extraction of 1-OHP from various polar sample solutions by a non-polar primary ESI solvent is identified and 1-OHP ionization efficiency strongly depends on the sample solution.